Respiratory syncytial virus (RSV), a common cause of winter
outbreaks of acute respiratory disease, results in an estimated
90,000 hospitalizations and 4500 deaths each year from lower
respiratory tract disease in both infants and young children in the
United States (1). Outbreaks occur annually throughout the country
(2). RSV activity in the United States is monitored by the National
Respiratory and Enteric Virus Surveillance System (NREVSS), a
voluntary, laboratory-based system. This report summarizes trends
in RSV from the NREVSS from July 1, 1990, through June 28, 1996,
and presents provisional surveillance results for June 29-November
29, 1996. These data indicate onset of widespread RSV activity for
the 1996-97 season.

Since July 1, 1990, a total of 98 hospital-based and public
health laboratories in 47 states have participated in the NREVSS
and have reported weekly to CDC the number of specimens tested for
RSV by the antigen-detection and virus-isolation methods and the
number of positive results. Widespread RSV activity is defined by
the NREVSS as the first of two consecutive weeks during which at
least half of the participating laboratories report any RSV
detections. This definition generally indicates a mean percentage
of specimens positive by antigen detection in excess of 10%.

During the previous six seasons, from July 1990 through June
1996, onset of widespread RSV activity began in November and
continued for a mean of 22 weeks until April (Figure_1). In
most
parts of the 48 contiguous states, activity peaked each year in
January or February; however, in the Southeast, activity peaked as
early as November or December (3). For the reporting period June
29-November 29, 1996, a total of 75 laboratories in 45 states
reported results of testing for RSV. Since the week ending November
22, more than half of the participating laboratories reported
detections of RSV on a weekly basis, indicating onset of widespread
RSV activity for the 1996-97 season.

Editorial Note

Editorial Note: During the RSV season, health-care providers should
consider the role of RSV as a cause of acute respiratory disease in
both children and adults. Most severe manifestations of infection
with RSV (e.g., pneumonia and bronchiolitis) occur in infants aged
2-6 months; however, children of any age with underlying cardiac or
pulmonary disease or who are immunocompromised are at risk for
serious complications from this infection. Because natural
infection with RSV provides limited protective immunity, RSV causes
repeated symptomatic infections throughout life. In adults, RSV
usually causes upper respiratory tract manifestations but may cause
lower respiratory tract disease -- especially in the elderly and in
immunocompromised persons (4-6). Infection in immunocompromised
persons can be associated with high death rates (6).

RSV is a common, but preventable, cause of nosocomially
acquired infection; the risk for nosocomial transmission increases
during community outbreaks. Sources for nosocomially acquired
infection include infected patients, staff, visitors, or
contaminated fomites. Nosocomial outbreaks or transmission of RSV
can be controlled with strict attention to contact-isolation
procedures (7). In addition, chemotherapy with ribavirin may be
considered for some patients (e.g., those at high risk for severe
complications or who are seriously ill with this infection) (8);
respiratory syncytial virus immune globulin intravenous (human) for
high-risk patients was licensed for use in January 1996 (9).
Vaccines for RSV are being developed, but none have been
demonstrated to be safe and efficacious (10).

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